Allyl halides, reaction with Grignard reagents

Primary halides (and some secondary cases) may be oxidized directly to carbonyl compounds by reaction with chromate ion, either in the presence of crown compounds, or with the chromate associated with a polymer matrix. Reduction of low molecular weight halides to hydrocarbons has been reported in superacid media [e.g. HF-TaFs), and a hydride transfer pathway is suggested. Allyl iodides may be reduced with triphenylphosphonium hydriodide (equation 10), but acid sensitive groups may not survive these conditions. Vinylic and aryl halides are converted into the parent hydrocarbons by reaction with Grignard reagents and a catalytic quantity of manganese salts a reaction mechanism has been proposed. 

Perfluoroaryl alkyl sulfides (e.g., 7) can be synthesized by the reaction of Grignard reagents with aryl halides in the presence of elemental sulfur. For example, allyl pentalluorophenyl sulfide (7) is obtained in excellent yield from bromopentafluorobenzene (5) and allyl bromide... 

Oxidative addition of the carbon-halogen bond is a well-documented reaction for Group 10 transition metal complexes, but it is relatively limited for ruthenium. The example given here involves the reversible oxidative addition of allyl halide to RuCp(CO)2X to produce RuCp(p -allyl)X2 [78]. Oxidative addition of allyl halide to a Ru(0) complex Ru(l,5-COD)(l,3,5-COT) is also reported, but the product yield was poor [79]. Nevertheless, a catalytic Heck-type alkenylation of bromostyrene with methyl acrylate by Ru(l,5-COD)(l,3,5-COT) proceeded smoothly [80]. A cross-coupling reaction of alkenyl halide with Grignard reagents or alkyl lithium also pro-... 

A useful method of preparing 1-alkenes involves reaction of Grignard reagents with the unusually reactive halide, allyl bromide ... 

Many alkynyl, alkenyl, aryl, and functionalised alkyl-lithiums behave well in alkylation reactions because they are more stable anions than those derived from the simple unfunctionalised alkyl halides with which they are to react. Examples are 24, 25, and 26 and these will be treated in later chapters with the reactions of Grignard reagents with allyl halides. 

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